Slip Assembly for Anchoring Downhole Plugs and Retainers

ABSTRACT

A downhole plug assembly can be installed at a desired location within a subterranean wellbore that is capable of isolating one portion of the wellbore from another, while sealing fluid pressure within the wellbore from at least one direction. The plug assembly can include certain components constructed of non-metallic material that can be drilled, milled or mechanically broken up more quickly and efficiently than conventional wellbore plugs, thereby facilitating removal of said plug assembly when desired.

CROSS REFERENCES TO RELATED APPLICATIONS

THIS APPLICATION CLAIMS PRIORITY OF UNITED STATES PROVISIONAL PATENT APPLICATION SERIAL NO. 62/373,419, FILED AUG. 11, 2016, INCORPORATED HEREIN BY REFERENCE.

STATEMENTS AS TO THE RIGHTS TO THE INVENTION MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT:

NONE

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention pertains to a downhole assembly including, without limitation, a drillable plug assembly that can be installed at a desired location within a subterranean wellbore. More particularly, the present invention pertains to a plug assembly that is capable of providing a fluid pressure seal within a wellbore, while being capable of being drilled, milled or mechanically broken up more efficiently than conventional wellbore plugs. More particularly, the present invention pertains to a plug that can permit selective fluid pumping through said plug (including, without limitation, as a cement retainer).

2. Brief Description of the Prior Art

Bridge plugs, retainers or other anchoring and/or sealing devices are frequently installed within subterranean wellbores such as oil and gas wells. Such assemblies can be installed to isolate one portion of a wellbore from another, to prevent fluid flow between segments of a wellbore, and/or to provide a fluid pressure sealing barrier within said wellbore. In most instances, said plugs are set inside the internal through bore of pipe that is installed within a wellbore (typically a casing or tubing string).

Conventional bridge plugs used to isolate one portion of a wellbore from another typically comprise at least one anchoring system that grips the inner surface of said surrounding wellbore and locks said plug in place against axial movement. Such plugs typically also include at least one expandable sealing/packing element that provides a fluid pressure seal against said internal wellbore surface (that is, between the outer surface of the plug and the inner surface of the surrounding wellbore). Cement retainers are similar to such bridge plugs, but also permit the selective pumping of cement slurry or other fluid through said devices; as used herein, the terms “plugs” or “bridge plugs” shall also include cement retainers.

Although many bridge plugs are designed to be permanently installed, certain other bridge plugs are designed to be removed by being drilled with a bit, mill or other device when isolation of a portion of a wellbore is no longer desired. Such conventional “drillable” bridge plugs are typically constructed of drillable cast iron, aluminum, non-metallic materials or some combination thereof; such drillable plugs can generally be drilled or milled faster and more efficiently than plugs that are constructed from metallic components.

Such conventional drillable bridge plugs are frequently difficult and time consuming to drill out, mill up or otherwise mechanically break apart. In certain applications, multiple drillable plugs are installed within a single wellbore. In such cases, the time (and associated cost) of drilling, milling or otherwise removing said multiple plugs is compounded.

Thus there is a need for a drillable plug that securely anchors in place within a wellbore and provides a reliable fluid pressure seal against the inner surface of said wellbore. When desired, said plug assembly should be capable of being drilled, milled or otherwise mechanically broken apart more easily and efficiently than conventional bridge plugs (including, without limitation, drillable bridge plugs).

SUMMARY OF THE INVENTION

In a preferred embodiment, the present invention comprises a slip assembly for use with downhole wellbore plugs and/retainers such as, for example, in oil or gas wells penetrating subterranean formations. In a preferred embodiment, certain components of the slip assembly of the present invention can be beneficially constructed, at least in part, from material(s) that can be relatively easily milled or drilled, such as, for example, non-metallic composite material (including, without limitation, glass filed epoxy resin) or other material exhibiting similar qualities and characteristics.

Said slip assembly of the present invention can be utilized with a fully sealing plug assembly. In operation, the slip assembly of the present invention can be attached to a conventional setting tool and conveyed into a well to a desired depth via continuous wire (such as, for example, electric line or slick one), coiled tubing or jointed pipe. Once said plug assembly has been placed at a desired location within said wellbore, said setting tool can be actuated to extend said at least one slip assembly outward to grip the surrounding wellbore. At least one sealing member (such as, for example, an elastomeric ring) can also extend outward to engage against and form a fluid pressure seal against the inner surface of the surrounding wellbore.

The assembly of the present invention allows for elimination of composite bands or other conventional retention devices typically used to hold slip members in place prior to setting/engagement of said slip members. Said bands or conventional retention devices can sometimes obstruct slips from properly anchoring to a casing wall. Further, such bands or other conventional retention devices can often become damaged/broken, allowing slip members to become detached and fall within a wellbore, thereby resulting in costly fishing operations and/or additional inherent risk of loss or damage. By eliminating said bands or conventional retention devices, the present invention eliminates such risk.

When desired, a plug assembly equipped with the slip assembly of the present invention can be drilled, milled or otherwise mechanically broken apart more easily and efficiently than conventional bridge plugs including, without limitation, drillable bridge plugs.

BRIEF DESCRIPTION OF DRAWINGS/FIGURES

The foregoing summary, as well as any detailed description of the preferred embodiments, is better understood when read in conjunction with the drawings and figures contained herein. For the purpose of illustrating the invention, the drawings and figures show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed in such drawings or figures.

FIG. 1 depicts a side perspective view of a slip assembly of the present invention in a non-engaged or “running-in” configuration.

FIG. 2 depicts a side perspective view of a slip assembly of the present invention in an engaged or “set” configuration within a partially cut-away section of casing.

FIG. 3 depicts a side sectional view of a portion of the slip assembly of the present invention operationally attached to a conventional setting tool while being run in a wellbore.

FIG. 4 depicts a side sectional view of a portion of the slip assembly of the present invention operationally attached to a conventional selling tool within a wellbore during an intermediate engagement step.

FIG. 5 depicts a side sectional view of a portion of the slip assembly of the present invention operationally attached to a conventional setting tool within a wellbore while being set.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 depicts a side perspective view of a slip assembly 100 of the present invention in a non-engaged or “running-in” configuration, such as when said slip assembly 100 comprises part of a downhole plug assembly and is being conveyed in a wellbore on wireline, continuous tubing or jointed pipe string. It is to be observed that slip assembly 100 can be installed in connection with a downhole plug assembly well known to those having skill in the art; such plug assembly can comprise multiple slip assemblies 100, as well as at least one elastomeric sealing member that can be selectively engaged to form a fluid pressure seal against the inner surface of a surrounding wellbore.

As depicted in FIG. 1, slip assembly 100 of the present invention comprises a plurality of wedge shaped slip members 10 operationally attached to push ring 20. Said wedge shaped slip members 10 are moveably disposed on inclined ramp surfaces 31 of cone member 30, although said slip members 10 can be selectively locked against movement as described herein. Slip members 10 have leading edge or end 11 and trailing end 12. Leading end 11 generally forms a tapered edge, while trailing end 12 has lateral dovetail extensions or projection members 13 that extend laterally outward from slip members 10. Wedge shaped slip members 10, push ring 20 and cone member 30 are disposed on a central mandrel, discussed in more detail below; in the embodiment depicted in FIG. 1, the upper portion of said central mandrel forms extension or collar 22.

Said dovetail projection members 13 are slidably received within matching mortise-like dovetail recesses 21 formed in push ring 20. Each of said dovetail projection members 13 can travel within recesses in a direction that is substantially normal to push ring 20 and the longitudinal axis of central mandrel 40. Wedge-shaped slip members 10 also have angled lateral ledge extensions 14 that are slidably received within tracks or grooves 32 of cone member 30; said tracks or grooves 32 are positioned adjacent, and oriented generally parallel, to inclined ramp surfaces 31 and run along the length of said ramp surfaces 31 on the sides of said ramp surfaces.

Dovetail projection members 13 on each slip member 10 keep said slip members operationally linked to push ring 20, and prevent said slip members 10 from moving in an axial direction apart from said push ring 20. Further, angled lateral ledge extensions 14 on the sides of slip members 10 keep said slip members 10 from extending radially outward while said slip assembly 100 is being conveyed in a well.

Slip assembly 100 of the present invention can include, but does not require composite bands or other conventional retention devices to hold slip members 10 in place prior to setting/engagement of said slip members (such as when said slip assembly 100 is being run into a well on wireline or pipe). As previously noted, said bands or conventional retention devices can sometimes obstruct slips from properly anchoring to a casing wall. Further, such bands or other conventional retention devices can often become damaged/broken, allowing slip members to become detached and fall within a wellbore, thereby resulting in costly fishing operations and/or additional inherent risk of loss or damage. By eliminating said bands or conventional retention devices, slip assembly 100 of present invention eliminates such risk.

FIG. 2 depicts a side perspective view of a slip assembly 100 of the present invention in an engaged or “set” configuration within a partially cut-away section of casing 200 having inner surface 201. As depicted in FIG. 2, during the setting process push ring 20 applies axial force on wedge-shaped slip members 10, causing said slip members 10 to ride along inclined ramp surfaces 31 (obscured from view in FIG. 2) of cone member 30 and, in turn, forcing outer surfaces 15 of said slip members 10 in a radially outward direction toward inner surface 201 of casing 200. In the configuration depicted in FIG. 2, upper cylindrical extension 22 faces generally up hole within casing 200.

Still referring to FIG. 2, as said slip members 10 extend radially outward, dovetail extensions or projection members 13 of said slip members 10 can radially protrude from dovetail recesses 21; however, said slip members 10 remain operationally linked to push ring 20 to prevent independent axial movement of said slip members 10 and push ring 20 relative to each other. Wickers or buttons 16 made of powdered metal and composite matrix material are molded in slip members 10 allowing said slip members 10 to grip or bite into said inner surface 201 of said casing 200 (including, without limitation, hardened pipe such as Q-125 casing).

FIGS. 3 through 5 depict a series of side sectional schematic views of a portion of the slip assembly 100 of the present invention during a running in, and engagement/setting sequence. Referring to FIG. 3, slip assembly 100 is attached to conventional setting tool 300 having outer setting sleeve 301; conventional setting tool 300 is well known to those having skill in the art Tapered or wedge-shaped slip member 10 is operationally attached to push ring 20, which is slidably disposed along the outer surface of central mandrel 40. Wedge shaped slip member 10 has outer surface 15 having powdered metal wickers or buttons 16 disposed thereon. As depicted in FIGS. 3 through 5, said buttons 16 are received within holes or apertures formed in spaced relationship along said outer surface 15 and at least partially extend beyond said outer surface 15. Inclined inner surface 17 of slip member 10 is disposed on inclined ramp surface 31 of cone member 30. In the configuration depicted in FIG. 3, push ring 20 is prevented from axial downward movement (during such running in operations) by at least one shear pin 23 constructed of material having a known or predetermined shear strength.

Referring to FIG. 4, after said slip assembly 100 has been conveyed to a desired location within a wellbore, conventional setting tool 300 is actuated causing opposing axial forces to act on push ring 20 and central mandrel 40. Prior to such actuation, shear phi 23 locks slip assembly 100 in the running position until said setting tool 300 is actuated; thereafter, setting sleeve 301 applies axial force to push ring 20, while central mandrel 40 is forced in the opposite axial direction or secured against said axial movement, thereby forcing shear pin 23 to shear or separate, effectively unlocking push ring 20 and permitting axial movement of said push ring 20. Once “unlocked”, push ring 20 can be axially moved toward cone member 30.

Referring to FIG. 5, setting sleeve 301 applies axial force to push ring 20 which, in turn applies axial force to wedge-shaped slip members 10. Such axial force causes said slip members 10 to interact with inclined ramp surfaces 31 of cone member 30, thereby driving outer surface 15 (and wickers or buttons 16 disposed thereon) of said slip member 10 in a radially outward direction. As said slip member 10 extends radially outward, said slip member 10 remains operationally linked to push ring 20 to prevent independent axial movement of said slip member 10 and push ring 20 relative to each other. Referring back to FIG. 2, when said slip members 10 are extended radially outward, buttons 16 disposed on the outer surfaces 15 of said slip members 10 can contact in gripping relationship with inner surface 201 of wellbore casing 200, thereby anchoring slip assembly 100 against axial movement within said wellbore.

During the setting process, leading ends 11 of slip members 10 ride along inclined ramp surfaces 31 of cone member 30, travelling in a direction that is substantially parallel to the longitudinal axis of central mandrel 40. As said slip members 10 travel along inclined ramp surfaces 31 said slip members 10 cooperate with said inclined ramp surfaces 31 and expand radially outward toward the inner surface of a surrounding tubular or wellbore. Angled lateral ledge extensions 14 of slip members 10 travel in grooves 32 that are oriented substantially parallel to inclined surface 31; said lateral ledge extensions 14 cooperate with said grooves 32 to ensure that slip members 10 remain engaged against ramp surfaces 31 of cone member 30. Trailing ends 12 of slip members 10 have dovetail projection members 13 that extend laterally outward from said slip members 10. Said dovetail projection members 13 are slidably received within mating dovetail recesses 21 in push ring 20.

A common problem with existing conventional cement retainer designs is that they typically utilize frangible bands or a full circular ring of steel slips that frequently break prior to the plug reaching a desired setting depth in a well. Such premature breakage causes the tool to inadvertently “pre-set”, which can require significant time and expense to remedy. By contrast, with the present invention, angled lateral ledge extensions 14 of slip members 10 travel in grooves 32, while dovetail projection members 13 at trailing ends 12 of slip members 10 are engaged into the mating dovetail recesses 21 of push ring 20. As a result, slip members 10 remain locked radially inward as push ring 20 is spread apart from cone member 30. This ensures that said slip members 10 are drawn tight inwardly against mandrel 40, and that said slip members 10 are held securely in place, during the running process and prior to desired setting of slip assembly 100 and engagement of said slip members 10 against a surrounding tubular or wellbore surface. Shear pin 23 acts to keep slip members 10 (such as the upper slip members of a plug assembly) from prematurely setting until setting tool 300 is activated. Said push ring 20 is typically one of the first components to move during the setting process.

The cooperating dovetail design of slip member 10 and push ring 20 also serves as an anti-rotational feature during the drilling process (such as when slip assembly 100 is being drilled or milled) and eliminates the need for conventional slip retaining rings. Additionally, upon drilling or milling of said slip assembly 100, drilled up components of said slip assembly 100 can be easily and conveniently circulated out of a wellbore using well fluids.

Notwithstanding anything to the contrary contained herein, all dimensions, specifications and material selections are illustrative only and are not intended to be, and should not be construed as, limiting in any way. Moreover, except for said powdered metal wickers and shear pins, ail other components of the slip assembly of the present invention can be constructed of composite or non-metallic material.

The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention. 

What is claimed:
 1. A slip assembly for gripping an internal surface of a wellbore comprising: a) a cone member having a plurality of recessed slots disposed in spaced relationship around the outer circumference of said cone member, wherein said recessed slots define inclined surfaces; b) a plurality of slip members, each having a leading end and a trailing end, wherein at least one slip member is slidably disposed within each of said recessed slots; and c) a push ring operationally linked to said slip members, wherein axial movement of said push ring toward said cone member causes said slip members to interact with said inclined surfaces and extend radially outward.
 2. The slip assembly of claim 1, wherein each of said slip members are wedge-shaped.
 3. The slip assembly of claim 2, wherein each wedge-shaped slip member is slidably disposed on an inclined surface of a recessed slot of said cone member,
 4. The slip assembly of claim 1, wherein each of said slip members further comprises at least one dovetail projection extending laterally from said slip member at said trailing end.
 5. The slip assembly of claim 4, wherein each of said dovetail projections is slidably disposed within an aligned recess in said push ring.
 6. The slip assembly of claim 5, wherein each dovetail projection travels within said aligned recess in a direction that is substantially normal to said push ring.
 7. The slip assembly of claim 1, wherein each of said slip members further comprises at least one lateral ledge member slidably disposed within an elongate track in said cone member.
 8. The slip assembly of claim 7, wherein each of said elongate tracks is oriented substantially parallel to an inclined surface of a recessed slot.
 9. The slip assembly of claim 1, further comprising at least one wicker or button disposed on an outer surface of at least one slip member.
 10. The slip assembly of claim 9, wherein said at least one wicker or button comprises powdered metal and composite matrix material.
 11. A slip assembly for gripping an internal surface of a wellbore comprising: a) an elongate central mandrel; b) a cone member disposed on said mandrel and having a plurality of recessed slots disposed in spaced relationship around the outer circumference of said cone member, wherein each of said recessed slots is oriented substantially parallel to the longitudinal axis of said central mandrel and defines an inclined surface; c) a push ring releasably attached to said central mandrel; and d) a plurality of wedge-shaped slip members slidably disposed within said recessed slots, wherein each slip member has a leading end, a trailing end, an outer surface, an inclined inner surface, and at least one dovetail projection extending laterally from said trailing end and moveably disposed within an aligned recess in said push ring oriented substantially normal to the longitudinal axis of said central mandrel.
 12. The slip assembly of claim 11, wherein axial movement of said push ring toward said cone member causes said inclined inner surfaces of said slip members to interact with said inclined surfaces of said recessed slots and extend radially outward toward said wellbore internal surface.
 13. The slip assembly of claim 11, wherein each of said slip members further comprises at least one lateral ledge member slidably disposed within an elongate track in said cone member.
 14. The slip assembly of claim 13, wherein each of said elongate tracks is oriented substantially parallel to an inclined surface of a recessed slot.
 15. The slip assembly of claim 11, further comprising at least one wicker or button disposed on an outer surface of at least one slip member.
 16. The slip assembly of claim 15, wherein said at least one wicker or button comprises powdered metal and composite matrix material.
 17. A slip assembly for gripping an internal surface of a wellbore comprising: a) an elongate central mandrel; b) a cone member disposed on said mandrel and having a plurality of recessed slots disposed in spaced relationship around the outer circumference of said cone member, wherein each of said recessed slots is oriented substantially parallel to the longitudinal axis of said central mandrel and defines an inclined surface; c) a push ring releasably attached to said central mandrel; and d) a plurality of wedge-shaped slip members, slidably disposed within said recessed slots, wherein each slip member has a tapered leading end, a trailing end, an outer surface, an inclined inner surface, at least one lateral ledge member slidably disposed within an elongate track in said cone member oriented parallel to an inclined surface of a recessed slot, and at least one dovetail projection extending laterally from said trailing end and moveably disposed within an aligned recess in said push ring oriented substantially normal to the longitudinal axis of said central mandrel.
 18. The slip assembly of claim 17, wherein axial movement of said push ring toward said cone member causes said inclined inner surfaces of said slip members to interact with said inclined surfaces of said recessed slots and extend radially outward toward said wellbore internal surface.
 19. The slip assembly of claim 17, further comprising at least one wicker or button disposed on an outer surface of at least one slip member.
 20. The slip assembly of claim 19, wherein said at least one wicker or button comprises powdered metal and composite matrix material. 